1. Field of the Invention
The present invention relates to an endless belt used for conveying chip components on a chip component feeding apparatus or the like and a method of manufacturing the same.
2. Description of the Prior Art
FIG. 5 shows an example of a chip component feeding apparatus using an endless belt. Referring to the figure, numeral 1 denotes a vertical passage, numeral 2 denotes a curved passage, numeral 3 denotes a transverse passage, numeral 4 denotes a stopper, numeral 5 denotes a component take-out port, numeral 6 denotes a pair of front and rear timing pulleys, numeral P denotes a chip component P, and numeral B denotes a timing belt.
The vertical passage 1 and the curved passage 2 have a passage shape matching the end-face shape of the chip component P, and allow the chip components P to move downward by self-weight in longitudinally aligned state. The passage shape of the vertical passage 1 and the curved passage 2 is rectangular in the transverse cross section when the chip component P has a flat prism shape, and square in the cross section when the chip component P has a square prism shape or a cylinder shape.
The transverse passage 3 has a passage shape similar to that of the vertical and curved passages 1 and 2, aligns and guides the chip components P which are conveyed forward by the timing belt B. The transverse passage 3 opens in its bottom surface, the opening being closed by the surface of the timing belt B. The transverse passage 3 is provided at its front end with the stopper 4 for stopping at a take-out position the chip components P transported forward by the timing belt B. In addition, the component take-out port 5 is provided behind the stopper 4, the port 5 having a sufficient size to take out the component.
The timing pulleys 6 are disposed at the front and rear portions of the transverse passage 3. The timing belt B is wound around the timing pulleys 6, and an upper flat section of the timing belt B movably contacts with the opening face in the transverse passage 3. One of the timing pulleys 6 is intermittently rotated by a predetermined angle in the counterclockwise direction in the figure by an intermittent drive mechanism (not shown) including a ratchet mechanism, whereby the upper flat section of the timing belt B is intermittently moved to the left in the figure by a predetermined distance.
The upper end of the vertical passage 1 leads to a component storage chamber (not shown) in which a large number of single kind of chip components P are stored in a bulk state. The chip components P in the component storage chamber go in the upper opening of the vertical passage 1 one by one in a longitudinally orientation, pass through the vertical passage 1 and the curved passage 2 by self-weight, and are discharged from the lower end of the curved passage 2 onto the surface of the timing belt B.
The chip components P discharged onto the surface of the timing belt B and conveyed forward by the intermittently advancing timing belt B. Since the intermittent advance of the timing belt B is repeated in a predetermined cycle, the chip components P in the curved passage 2 are successively discharged onto the surface of the timing belt B. The discharged chip component P is moved forward in a longitudinally aligned state together with the timing belt B while being aligned by the transverse passage 3.
When a forefront chip component P among the chip components P moving forward together with the timing belt B touches the stopper 4, the succeeding chip components P are also stopped in a manner following the forefront one, whereby the forefront one can be taken out from the component take-out port 5.
Thereafter, every time the forefront chip component P is taken out from the take-out port 5 by a suction nozzle (not shown), the timing belt B is intermittently moved forward by the predetermined distance, and then the following chip component P again touches the stopper 4, and can be taken out.
By the way, the above chip component feeding apparatus utilizes the upper flat section of the timing belt B wound around a pair of front and rear timing pulleys 6 for conveying the chip components P, and the chip components P are taken out on the upper flat section near the front timing pulley 6.
For such a kind of the timing belt B, JIS standards prescribe accuracy of tooth height at .+-.0.2 mm. When the chip component P to be conveyed has a large size, there is no particular difficulty even if the timing belt B with such dimensional accuracy is used. However, when the chip component P becomes to have a minute size, there arises the following difficulty.
More specifically, when the timing belt B used has .+-.0.2 mm height accuracy of a tooth Ba, there intermix, as shown in FIG. 6 (a), tooth Ba with a reference height t, higher tooth Ba with height t1 which is larger than the reference height t by up to 0.2 mm, and lower tooth Ba with height t2 which is smaller than the reference height t by up to 0.2 mm.
That is, assuming that the surface height of the timing belt is Ht when the tooth Ba with the reference height t meshes the timing pulley 6, as shown in FIG. 6(b), the surface height of the timing belt B is Ht1 higher than Ht by 0.2 mm when the tooth Ba with height t1 (&gt;t) meshes the timing pulley 6, and is Ht2 lower than Ht by 0.2 mm when the tooth Ba with height t2 (&lt;t) meshes the timing pulley 6.
Therefore, when the minute chip component P, for example, the chip component P with thickness or diameter of 1 mm or less is conveyed by the timing belt B, the surface height of the timing belt B would be varied at the component take-out position by about one half of the thickness or diameter of the chip component P at the maximum. Then, similar height variations appear on the chip components P at the component take-out position, so that it may tend to failure in taking out the components by the suction nozzle.
Such difficulty also occurs when the component take-out position is shifted backward from the front timing pulley 6 and the upper flat section of the timing belt B is supported by a belt guide 7, as shown in FIG. 6(c). In particular, if there is only a small clearance between the timing belt B and the belt guide 7, the teeth may contact the belt guide 7, causing similar height variations on the chip components P during transport, whereby failure occurs in conveying.